Rectifiers for AC to DC conversion of high frequency signals have been well known for decades. A particular type of diode rectifier when coupled to an antenna, called a Rectenna, has also been known for decades. More specifically, over 20 years ago, Logan described using an array of Rectennas to capture and convert microwaves into electrical energy in U.S. Pat. No. 5,043,739 granted Aug. 27, 1991. However, the dimensions of the antenna limited the frequency until recently, when Gritz, in U.S. Pat. No. 7,679,057 granted Mar. 16, 2010, described using a similar structure for converting infrared light into electricity, and Pietro Siciliano suggested that such a structure may be used for sunlight in “Nano-Rectenna For High Efficiency Direct Conversion of Sunlight to Electricity: by Pietro Siciliano of The-Institute for Microelectronics and Microsystems IMM-CNR, Leece (Italy).
Still, the minimum dimensions required for such visible light rectennas are generally in the tens of nanometers. While these dimensions can be accomplished by today's deep submicron masking technology, such processing is typically far more expensive than the current solar cell processes, which require much larger dimensions.
Still, as Logan pointed out in U.S. Pat. No. 5,043,739, the efficiency of microwave Rectennas can be as high as 40%, more than double that of typical single-junction poly-silicon solar cell arrays, and when using metal-oxide-metal (MOM) rectifying diodes, as Pietro suggests, no semiconductor transistors are needed in the array core.
As such, it may be advantageous to be able to utilize the existing fine geometry processing capability of current semiconductor fabrication without incurring the cost of such manufacturing.